An important technical task in industrial production and automation, in metrology, in road traffic, in safety engineering, environmental technology and many additional fields, consists of obtaining, via the propagation of signal waves, i.e. contact-less by means of wave propagation either passively (externally-generated signal waves) or actively (self-generated signal waves), information about the signal waves themselves and in particular about their sources or about objects which have modified the waves by reflection or transmission, in particular in the phase and amplitude. Measuring systems for such tasks have long been known, in particular laser radars for optical signal waves, microwave radars for microwaves, ultrasonic sonars for sonic waves and computer tomographs for X-rays. The preferably self-generated signal waves of a signal source are preferably modulated in suitable manner. If this modulation of a “carrier signal” is modified in phase and amplitude by the preferably multi-dimensional objects to be measured, object information can be obtained by suitable demodulation of the transmitted and reflected signal waves, e.g. the shape of a three-dimensional object by multipoint/multipixel measurement. The associated receiving apparatus is very expensive and generally only contains one receiver. However in order to measure many measuring points on the signal wave, it uses a scanner. The state of the art for optical signal waves is described e.g. on page 463 ff in “Handbook of Computer Vision and Applications”, Volume 1, Sensors and Imaging, edited by Jähne et al, Academic Press. There, a novel solution for simplification of the optical receiver is described, the “photonic mixer device” (PMD), which is described for the first time in DE 196 35 932.5.
The photocharges generated in the PMD by the incident modulated light wave are, according to the state of the art, exposed to a demodulating oscillation process by means of at least two photogates and read out and evaluated in the push-pull, reducing the expenditure on, and size of the receiver by orders of magnitude, which makes possible the construction of an array producing images from many pixel-type receivers. In spite of this exceptional progress, such PMD pixel receivers have disadvantages: The modulating photogates cause an attenuation of the incident light. Moreover, the modulating electrical drift field is not optimally introduced into the flow direction of the photocharge. The modulation bandwidth of the modulation of the photocurrent distribution by means of this modulation photogate is practically limited to approximately 1 GHz. Furthermore, an essential sensitivity increase by corresponding design of these known CMOS modulation photogate PMDs using a charge carrier multiplication by impact ionization (avalanche effect) or other secondary electron multiplication is scarcely realizable.
Novel solutions are needed for photonic mixer devices without modulation photogates with, in particular, higher modulation bandwidths and accuracy and higher sensitivity.